Field of the Invention
The invention relates to a multi-phase transformer having a superconductive toroidal winding.
In the case of transformers for high powers, the use of superconductive materials for conductors of windings is known in order to achieve low weights and losses. Configurations without iron, that is to say without a transformer core, are preferably used in that case. In order to avoid a magnetic field which is emitted into the environment of the transformer, the winding itself forces the main field to be guided as far as possible in closed flux loops for reasons of electromagnetic compatibility (EMC).
One known solution to that problem is the toroidal winding, in which favorable guidance of the main field is possible. The toroidal winding in that case is produced from a tube-like material. Such a toroidal winding requires a complex manufacturing technique. In order to achieve the superconductivity, the toroidal winding is accommodated in a cryostat vessel, in particular a tank or any other suitable vessel, which contains a cooling medium. Such superconductive transformers have heretofore only existed in practice as trial models, in a single-phase structure.
A superconductive transformer which is disclosed in Swiss Patent 411 124 has windings disposed in a toroidal shape and cross sections of the windings have an annular shape. German Published, Non-Prosecuted Patent Application 1 488 322 discloses a transformer having superconductive windings, in which windings that are interleaved coaxially in one another are disposed on a common core which is closed in an annular shape. In addition, a direct current winding is provided which is divided into winding elements in such a manner that voltages which are induced in it because of alternating fluxes in the magnetic circuit cancel one another out.
German Published, Prosecuted Patent Application 1 204 322 discloses a three-phase transformer having windings disposed in a known manner on a five-limbed core. The core is constructed from three parts. Each core part is assigned one separate container in each case, and each container is provided with a flange. The transformer can be disassembled, with its core and container parts, for the purpose of transportation.